On 4/11/2018 7:21 AM, mike wrote:> > There are plenty of disasters waiting to happen. There's little > reason to purposely introduce others. Saying things like, "nothing > serious happens if the FET is destroyed," just adds insult to injury. >You keep harping on about that statement of mine without acknowledging the context. This is very different from what you said in another thread. Let's see - "Probably...." "I had one fixture that seemed to work, but...." "Plug one in and try it" "I've had some success...." doesn't sound like you need to be 300% sure of everything before actually doing it.
Exceeding Vgs rating
Started by ●April 6, 2018
Reply by ●April 11, 20182018-04-11
Reply by ●April 11, 20182018-04-11
On 4/11/2018 1:09 AM, John Larkin wrote:> On Tue, 10 Apr 2018 17:01:13 +0100, Clive Arthur > <cliveta@nowaytoday.co.uk> wrote: > >> On 06/04/2018 20:18, mike wrote: >> >> <snip> >> >>> You guys talk like ignoring specifications is acceptable practice. >>> IT IS NOT! >>> Testing a few samples under controlled conditions is NOT reason to >>> exceed specifications. >> >> Oh dear. My latest design has microprocessors, FPGAs and lots of analog >> stuff, almost all of which will be used outside the manufacturer's >> specifications, in some cases way outside. Luckily, the customers are >> aware of this. >> >> The connectors and the PCB are within spec though. Phew. >> >> Cheers > > That is NOT ACCEPTABLE and you are a BAD PERSON. >You guys crack me up. Golly gosh and gadzooks! You scoundrels are being unpleasant to another person. :-) This reminds me of a story I read in Archie comics some time ago (yes, I still read them). Principal Weatherbee caught Archie using the word 'lousy' and chided him for using a crude expression. Archie watched his words for awhile and was tormented by his friends who bombarded him with excessively staid language until Weatherbee relented. Maybe I should start cussing a bit.
Reply by ●April 11, 20182018-04-11
On 11/04/2018 02:51, mike wrote: <snipped>> If you're exceeding the breakdown voltage specs of your FPGAs and > microprocessors > by a large margin (way outside), you must be a lucky designer. > Even the worst of the clueless designers I've known knew better.It's hole-in-the-ground stuff and it's the temperature specs that are routinely exceeded, because otherwise you couldn't do the job and short equipment lifetimes are the norm. Most other specs are treated very conservatively. Previously unused devices are tested of course, and each designer or team has an inventory of parts which are known to work and even parts of parts which don't work. That's valuable information. The fun starts when a manufacturer moves, for example, to a different process and doesn't mention it because it doesn't change the spec. Cheers -- Clive
Reply by ●April 11, 20182018-04-11
On 10/04/2018 20:39, John Larkin wrote:> On Tue, 10 Apr 2018 17:01:13 +0100, Clive Arthur > <cliveta@nowaytoday.co.uk> wrote: > >> On 06/04/2018 20:18, mike wrote: >> >> <snip> >> >>> You guys talk like ignoring specifications is acceptable practice. >>> IT IS NOT! >>> Testing a few samples under controlled conditions is NOT reason to >>> exceed specifications. >> >> Oh dear. My latest design has microprocessors, FPGAs and lots of analog >> stuff, almost all of which will be used outside the manufacturer's >> specifications, in some cases way outside. Luckily, the customers are >> aware of this. >> >> The connectors and the PCB are within spec though. Phew. >> >> Cheers > > That is NOT ACCEPTABLE and you are a BAD PERSON.I know. I'll use FR4 and Molex from now on :-) Cheers -- Clive
Reply by ●April 11, 20182018-04-11
On Wed, 11 Apr 2018 09:02:15 +0100, Clive Arthur <cliveta@nowaytoday.co.uk> wrote:>On 10/04/2018 20:39, John Larkin wrote: >> On Tue, 10 Apr 2018 17:01:13 +0100, Clive Arthur >> <cliveta@nowaytoday.co.uk> wrote: >> >>> On 06/04/2018 20:18, mike wrote: >>> >>> <snip> >>> >>>> You guys talk like ignoring specifications is acceptable practice. >>>> IT IS NOT! >>>> Testing a few samples under controlled conditions is NOT reason to >>>> exceed specifications. >>> >>> Oh dear. My latest design has microprocessors, FPGAs and lots of analog >>> stuff, almost all of which will be used outside the manufacturer's >>> specifications, in some cases way outside. Luckily, the customers are >>> aware of this. >>> >>> The connectors and the PCB are within spec though. Phew. >>> >>> Cheers >> >> That is NOT ACCEPTABLE and you are a BAD PERSON. > >I know. I'll use FR4 and Molex from now on :-) > >CheersThe way that you tell if an FPGA is fast enough is to crank up the speed until it breaks, and then back off some. Are you not using FR4 now? -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●April 11, 20182018-04-11
On 11/04/2018 17:54, John Larkin wrote:> On Wed, 11 Apr 2018 09:02:15 +0100, Clive Arthur > <cliveta@nowaytoday.co.uk> wrote: > >> On 10/04/2018 20:39, John Larkin wrote: >>> On Tue, 10 Apr 2018 17:01:13 +0100, Clive Arthur >>> <cliveta@nowaytoday.co.uk> wrote: >>> >>>> On 06/04/2018 20:18, mike wrote: >>>> >>>> <snip> >>>> >>>>> You guys talk like ignoring specifications is acceptable practice. >>>>> IT IS NOT! >>>>> Testing a few samples under controlled conditions is NOT reason to >>>>> exceed specifications. >>>> >>>> Oh dear. My latest design has microprocessors, FPGAs and lots of analog >>>> stuff, almost all of which will be used outside the manufacturer's >>>> specifications, in some cases way outside. Luckily, the customers are >>>> aware of this. >>>> >>>> The connectors and the PCB are within spec though. Phew. >>>> >>>> Cheers >>> >>> That is NOT ACCEPTABLE and you are a BAD PERSON. >> >> I know. I'll use FR4 and Molex from now on :-) >> >> Cheers > > The way that you tell if an FPGA is fast enough is to crank up the > speed until it breaks, and then back off some. > > Are you not using FR4 now? > >Polyimide, 200'C rated. FR4 will last a short while for prototypes. Cheers -- Clive
Reply by ●April 11, 20182018-04-11
On Wednesday, 11 April 2018 17:54:49 UTC+1, John Larkin wrote:> The way that you tell if an FPGA is fast enough is to crank up the > speed until it breaks, and then back off some. >A long time ago I needed to use a TMS320C52 DSP outside its rated specs. TI were kind enough to give me some test code that exercised the known critical timing paths so that I could test the devices myself. I put the code in the boot path, so that each device was auto-tested every time it was used. This worked very nicely. John
Reply by ●April 11, 20182018-04-11
On 4/11/2018 1:02 PM, jrwalliker@gmail.com wrote:> On Wednesday, 11 April 2018 17:54:49 UTC+1, John Larkin wrote: > >> The way that you tell if an FPGA is fast enough is to crank up the >> speed until it breaks, and then back off some. >> > A long time ago I needed to use a TMS320C52 DSP outside its rated > specs. TI were kind enough to give me some test code that exercised > the known critical timing paths so that I could test the devices > myself. I put the code in the boot path, so that each device was > auto-tested every time it was used. This worked very nicely. > > John > > >THAT'S HOW IT'S DONE! You GUARANTEE that each device works in the application. The marginal cost of that test is almost zero. YOU take responsibility for the vendor's ability to supply parts that work. That calculated risk may cost you in the long run, but the customer gets a quality product. You consider the consequences early in the design phase and ENGINEER ways to make it work. That's the mindset you want in all of your design engineers. That's a far cry from the context of this thread as detailed in the subject line: asking random internet denizens if it's OK to exceed some voltage breakdown spec on some unspecified component by some nondescript amount. I stand by my original statements in this context, "NO, it ain't OK!"
Reply by ●April 11, 20182018-04-11
On 4/10/2018 9:27 PM, Pimpom wrote:> On 4/11/2018 7:21 AM, mike wrote: >> >> There are plenty of disasters waiting to happen. There's little >> reason to purposely introduce others. Saying things like, "nothing >> serious happens if the FET is destroyed," just adds insult to injury. >> > > You keep harping on about that statement of mine without acknowledging > the context. This is very different from what you said in another > thread. Let's see - > > "Probably...." > "I had one fixture that seemed to work, but...." > "Plug one in and try it" > "I've had some success...." > > doesn't sound like you need to be 300% sure of everything before > actually doing it."Another thread" is the definition of different context. I can't tell which thread/context to which you refer. I will say that diagnostic experiments aimed to determine what features are compatible or what has failed are not the same as ENGINEERING a product. When you run out of standard diagnostic options, random non-destructive testing may increase insight. In the newsgroups, you often see a lot of arguments over whether this USB device that I have in my hand might do what I want when just plugging in the device would answer the question. If I ever stated that it was OK to exceed specified breakdown voltages in a production device, I hereby retract that statement, offer sincere apologies for my error and vow to do my best to prevent such an irresponsible act in the future.
Reply by ●April 12, 20182018-04-12
On Wed, 11 Apr 2018 18:17:58 -0700, mike <ham789@netzero.net> wrote:>On 4/11/2018 1:02 PM, jrwalliker@gmail.com wrote: >> On Wednesday, 11 April 2018 17:54:49 UTC+1, John Larkin wrote: >> >>> The way that you tell if an FPGA is fast enough is to crank up the >>> speed until it breaks, and then back off some. >>> >> A long time ago I needed to use a TMS320C52 DSP outside its rated >> specs. TI were kind enough to give me some test code that exercised >> the known critical timing paths so that I could test the devices >> myself. I put the code in the boot path, so that each device was >> auto-tested every time it was used. This worked very nicely. >> >> John >> >> >> >THAT'S HOW IT'S DONE! You GUARANTEE that each device works in the >application. > >The marginal cost of that test is almost zero. > >YOU take responsibility for the vendor's ability to supply parts that >work. That calculated risk may cost you in the >long run, but the customer gets a quality product. > >You consider the consequences early in the design phase and ENGINEER >ways to make it work. >That's the mindset you want in all of your design engineers. > >That's a far cry from the context of this thread as detailed in the >subject line: asking random internet denizens if it's OK >to exceed some voltage breakdown spec on some unspecified >component by some nondescript amount. > >I stand by my original statements in this context, "NO, it ain't OK!"Well, arrest the OP. I think he's in India. -- John Larkin Highland Technology, Inc lunatic fringe electronics
